Zinc Anodes Modified by One‐Molecular‐Thick Self‐Assembled Monolayers for Simultaneous Suppression of Side‐Reactions and Dendrite‐Formation in Aqueous Zinc‐Ion Batteries

Repeated charge/discharge in aqueous zinc-ion batteries (ZIBs) commonly results in surface corrosion/passivation and dendrite formation on zinc anodes, which is a major challenge for the commercialization of zinc-based batteries. In this work, metallic Zn modified by self-assembled monolayers is described as a viable anode for ZIBs. ω-mercaptoundecanoic acid that is spontaneously adsorbed on Zn (MUDA/Zn) contributes to the simultaneous suppression of side reactions and dendrite formation in ZIBs. Though one-molecular-thick, densely packed alkyl chains prohibit H₂ O and H⁺ from making direct contact with the underlying Zn, and surface carboxylate moieties (-COO^- ) effectively repel anionic species (OH^- ) in a solution, which renders a Zn anode inert against zincate formation within a wide range of pH. In contrast, the electrostatic attraction between surface-carboxylates and cations increases the concentration of Zn²⁺ on the surface of MUDA/Zn to facilitate Zn plating/stripping with less overpotentials. The high concentration of Zn²⁺ also results in an increased number of nucleation sites, which enhances the lateral growth of Zn with no formation of dendrites. As a result, MUDA/Zn shows excellent stability during prolonged Zn plating/stripping within a wide range of pH. The advantageous properties of MUDA/Zn are also retained in full-cells coupled with δ-MnO₂ cathodes.